If you’ve been prescribed tamoxifen (Soltamox), you may wonder if there’s a specific time of day you should take it. Sometimes, the time of day you take a medication can affect how well that medication works and your risk of side effects.

Researchers have recently looked more closely at whether taking endocrine therapy medications such as tamoxifen in the morning or evening affects side effects and quality of life.

Although some newer studies suggest that the timing of treatment may influence how some people feel while taking therapy, there is still no official recommendation on what time of day is best for taking it.

Still, there are factors to think about when deciding the right time to take tamoxifen. This article will review those factors and general drug information to help you figure out the best time of day to take your tamoxifen as part of your breast cancer treatment plan.

What Is Tamoxifen?

Tamoxifen is a hormonal therapy used to treat hormone receptor-positive (HR-positive) breast cancer. You may take tamoxifen either as a treatment for breast cancer or as prevention, if you have a high risk of developing it. You can take tamoxifen whether or not you have been through menopause.

For treating early breast cancer, most people take it for five years, though some people continue taking it for up to 10 years. People who take it to reduce their risk of breast cancer also usually do so for about five years.

Tamoxifen helps reduce the risk of new or recurrent breast cancer by blocking the effect of estrogen on breast cancer cells. In HR-positive breast cancer, estrogen can encourage growth of cancer cells. By blocking estrogen, tamoxifen can slow or stop the growth signals estrogen sends.

How Should You Take Tamoxifen?

You should take tamoxifen exactly as your doctor instructs you to take it — don’t take more or less than prescribed.

Tamoxifen comes as a tablet or a solution that you take orally. If you take the tablet, you should swallow it whole — don’t break, crush, or chew it. If you take the solution, make sure to use the provided dosing cup.

What Members Are Saying

“I take it right before bed. Any other time, and I think I might forget a dose here and there. I keep the bottle right by my bed and take a glass of water with me as part of my nighttime routine.”

“To tell you the truth, I’ve taken it both morning and evening and do not notice any difference. I was so worried about the side effects before taking it. You never know how your body will react until you start.”

“I started taking it at night but then switched to morning. I haven’t experienced many symptoms — only once in a while, I get angry for no reason.”

“I started taking 20 milligrams in the morning, but it made me nauseous and I had trouble eating. I lost about 5 pounds that I didn’t really need to lose, so I switched to taking it at night.”

Tamoxifen is usually taken once or twice a day, at the same time each day. You can take tamoxifen with or without food. Ask your oncology team about consuming grapefruit or grapefruit juice while taking tamoxifen. Grapefruit may affect how the body processes (metabolizes) the medication.

It’s also important to tell your doctor or pharmacist about all medications you take, including antidepressants. Some antidepressants can interfere with the way tamoxifen is converted into its active form in the body, and certain options may not be preferred while taking tamoxifen.

Does Time of Day Matter?

The time of day you take tamoxifen doesn’t have a significant impact on how well it works.

A small study looked at the effects of taking the drug at different times of the day. Even though there were some small differences, the researchers concluded that time of day wouldn’t impact how well tamoxifen worked.

More recent research has expanded on this question. Studies published in 2024 and 2025 examined whether taking endocrine therapy in the morning or evening affects symptoms, treatment tolerability, and quality of life.

Some findings suggest that changing the timing of treatment may help certain people manage side effects, but the evidence is still developing.

At this time, major treatment guidelines do not recommend a specific time of day for everyone taking tamoxifen. The most important factor is taking it consistently as prescribed.

What Are the Possible Side Effects of Tamoxifen?

The type and severity of side effects of tamoxifen are different for everyone. The most common side effects include:

• Hot flashes (also known as hot flushes, sweats)
• Fatigue or excessive tiredness
• Vaginal discharge
• Vaginal bleeding
• Hair thinning
• Dry skin
• Depression
• Mood swings
• Nausea
• Constipation
• Fluid retention

You may experience a few or none of these side effects, but you likely won’t get all of them.

Important Safety Warning: When To Call Your Doctor

Most tamoxifen side effects are manageable, but some can be serious. Contact your doctor right away or seek emergency medical care if you experience:

• Signs of a blood clot, such as swelling, pain, warmth, or redness in one leg
• Sudden shortness of breath, chest pain or coughing up blood, which may be signs of a pulmonary embolism (blood clot in the lungs)
• Unusual vaginal bleeding, bleeding after menopause, or other unexpected changes in vaginal discharge
• Symptoms of a stroke, such as sudden weakness on one side of the body, difficulty speaking, severe headache, or vision changes

Tamoxifen can slightly increase the risk of blood clots and cancer of the lining of the uterus (endometrial cancer). Although these complications are uncommon, it’s important to recognize warning signs and report them promptly.

How To Choose When To Take Tamoxifen

The time of day you take tamoxifen therapy is a personal decision. With this medication, you don’t need to consider a specific time of day or meal times, but there are some other factors that may help you choose what time of day works better for you.

Make sure to talk to your oncologist or other health care provider before changing the time of day you take tamoxifen. It’s important to take your medication exactly as instructed.

Consider Your Other Medications

If you are premenopausal, you may take tamoxifen and other cancer drugs as a way to stop your ovaries from working and producing estrogen. This is known as ovarian suppression. You might also take medications, vitamins, or supplements for other medical conditions.

When thinking about what time to take tamoxifen, ask yourself if any of your other medications need to be taken:

• At a specific time of day
• With food
• On an empty stomach
• Separate from other medications

Since tamoxifen doesn’t have strict rules about when it should be taken, you can choose a time to take it that works with your other medications.

Look at Your Schedule

The best time to take tamoxifen is when you remember to take it. You can incorporate your tamoxifen into your schedule whenever it works best for you.

MyBCTeam members have shared what works best for them. One member shared, “I take it right before bed. Any other time, and I think I might forget a dose here and there. I keep the bottle right by my bed and take a glass of water with me as part of my nighttime routine.”

Another member who takes their tamoxifen in the morning shared, “I have a system, I was put on Caltrate 600+D for bones, potassium, and magnesium for muscle cramping and tamoxifen. I set the tamoxifen on top of my Caltrate bottle on my bathroom sink, and first thing in the morning, I take everything so I don’t forget.”

Observe Your Side Effects

While researchers have not found strong evidence that tamoxifen at a specific time of day improves cancer outcomes, in one study participants reported that changing the time they took tamoxifen affected the timing and severity of hot flashes.

Newer studies suggest that some people may feel better when taking it at a different time of day. However, doctors do not yet recommend one specific time that is best for everyone.

MyBCTeam members have shared how the time of day they take their medications can affect their side effects. One member started off taking it in the mornings but then switched to nighttime. They shared, “I started taking 20 milligrams in the morning, but it made me nauseous and I had trouble eating. I lost about 5 pounds that I didn’t really need to lose, so I switched to taking it at night.”

Another member shared, “I started taking it at night but then switched to morning. I haven’t experienced many symptoms — only once in a while, I get angry for no reason.”

A third member said, “I sleep better if I take it in the morning.”

Some people don’t notice a difference in side effects whether they take it in the morning or evening. Another MyBCTeam member commented, “To tell you the truth, I’ve taken it both morning and evening and do not notice any difference. I was so worried about the side effects before taking it. You never know how your body will react until you start.”

For many people, the best approach is to choose a time that fits their routine and stick with it. If you are experiencing bothersome side effects, ask your oncology team whether changing the timing of your dose may be worth trying.

Join the Conversation

On MyBCTeam, people share their experiences with breast cancer, get advice, and find support from others who understand.

Do you take your tamoxifen in the morning or at night? Have you noticed a difference in how you feel? Let others know in the comments below.